Since February 1995, 59 patients with recent aneurysmal SAH have been randomised in our study program, either for surgical aneurysm clipping or for endovascular treatment with Guglielmi detachable coils, to compare the safety and long-term efficacy of these methods. Patients with expansive haematomas or those in a moribund state were excluded, as well as those with aneurysms unsuitable for treatment with both methods. We used single photon emission tomography (SPET) to compare regional cerebral blood flow (rCBF) in surgically and in endovascularly-treated patients. In a sub-study presented in this paper, we analysed the data of patients in Grade I-III (Hunt & Hess) with anterior circulation aneurysms (n = 21). When changes between the pre- and post-treatment rCBF were compared, the surgically treated group showed a tendency towards improved rCBF (change in different vascular territories varied from +4% to +12%) while the endovascularly-treated group showed no consistent change (changes varied from -3% to +6%). There was, however, no significant statistical difference between the changes in the groups. Our results are preliminary, but they suggest that endovascular treatment of anterior circulation aneurysms may not have any advantage over surgical treatment in respect to disturbances in the rCBF.